Soil compaction in the top 12 inches of the soil (surface compaction) adversely affects soybean yields by limiting root growth, reducing nodulation, inhibiting potassium and phosphorus uptake and promoting diseases such as sudden death syndrome and Phytophthora root and stem rot. A long-term study conducted in Minnesota showed that the effect of surface compaction on soybean yields was correlated to soil moisture and soil phosphorus levels. When less than 14 inches of rain occurred between the first of May and the first of September, soybean yields were greater in the tracked rows. When more than 14 inches of rain occurred between the first of May and the first of September, soybean yields were lower in the tracked rows. Inflating your tires to the proper pressure is an easy and effective way to reduce surface compaction.

Take soil samples for nutrient and pH analysis

Maintain soil pH between 6.3 and 6.5 to maximize nutrient availability and biological nitrogen fixation while minimizing soybean cyst nematode population growth. Researchers from the University of Wisconsin and Iowa State University found that soybean cyst nematode populations increased significantly at soil pH levels greater than 6.5. When soil pH levels exceed 6.5, manganese deficiency symptoms can occur in lakebed and outwash soils. Maintain soil phosphorus levels above 20 ppm and soil potassium levels above the critical levels for your soil types. The critical level for potassium is calculated by multiplying your soil’s cation exchange capacity (CEC) by 2.5 and adding 75. For example, the critical potassium level for a soil having a CEC of 12 meq/100gm is 105 ppm [(12 x 2.5) + 75]. Avoid fall applications of potassium fertilizer to coarse-textured soils having CEC’s less than 6 meq/100 gm and organic soils to prevent leaching losses.

Collect and submit soil samples for soybean cyst nematode analysis

Soybean cyst nematodes (SCN) cause more economic losses than any other soybean pest. Yield losses up to 15 bushels per acre can occur before symptoms are visible. Collecting and submitting soil samples in the fall before planting soybeans is the first step to reducing yield losses from SCN. The Michigan Soybean Checkoff will cover the cost of up to 20 nematode samples per farm per year. For more information, please refer to the fact sheet on sampling for soybean cyst nematodes available online at http://www.michigansoybean.org/.

Select high-yielding, well-adapted varieties

Variety selection is one of the most important management decisions producers make. On average, the highest-yielding varieties in the MSU soybean variety trials produce five bushels per acre more than the overall average yield for the trials. Utilize the Michigan Soybean Performance Report, information from seed companies and your on-farm trials to select high-yielding, well-adapted varieties. Consider the following characteristics: yield, SCN resistance, disease resistance or tolerance, lodging resistance and maturity.

This article was produced by the SMaRT project (Soybean Management and Research Technology) a partnership between Michigan State University Extension and the Michigan Soybean Checkoff program, SMaRT was developed to help Michigan producers increase soybean yields and farm profitability.